The present invention generally relates to apparatus for the temporary storage and measured feeding of the volatile fuel components present in the free space of a fuel tank into the intake manifold of an internal combustion engine. The apparatus includes a vent line which connects the free space of the fuel tank to the atmosphere. Along this vent line there is disposed a storage chamber containing an absorption element, as well as at least one line connecting the storage chamber to the intake manifold. This line can be shut by an electromagnetically actuated valve which has at least one inlet port and at least one outlet port and a valve seat therebetween which can selectively be sealed by a closing element. More particularly, the present invention relates to improvements in these devices.
Apparatus of this type is disclosed in German Patent 38 02 664, which corresponds to U.S. Pat. No. 4,901,702, the contents of which are herein incorporated by reference. In this apparatus, an auxiliary valve that can be closed by a vacuum advance mechanism and which has a control chamber is located between an electromagnetically actuated valve and the intake manifold. At low engine operating speeds or when the carbon activated absorption element of this device is saturated with vapors, an excessively rich fuel-air mixture may be drawn into the engine. In order to prevent this occurrence, the apparatus employs an auxiliary valve that is connected in series directly in front of a non-return valve. The auxiliary valve comprises a vacuum advance mechanism which consists of a rubber-elastic adjustable membrane and a compression spring, the auxiliary valve having a separate closing element which rests at one end with a support collar against the adjustable membrane and at the other end against the compression spring. During low engine operating speeds in the near idling range, the flow rate of volatile fuel components through the apparatus is reduced so as to prevent the excessive enrichment of the mixture fed to the engine; at high engine operating speeds when the differential pressure between the engine and the tank is reduced, the non-return valve employed is wide open.
This apparatus consists of a large number of individual parts which add to the cost of its manufacture. Due to the large number of individual movable parts employed, the probability of a malfunction occurring rises during long periods of use, which can lead to impairment of the operation of the internal combustion engine to which it is connected.
Another device similar to this general type is disclosed in German Patent 41 00 659 (which corresponds to Canadian Patent Application 2,058,819, the contents of which are incorporated herein by reference). This device employs a series of sensors to monitor the operation of the system by transmitting values concerning a number of selected parameters to a diagnostic unit, where the measured values are compared against a series of predetermined target values.
There remains a need for the further development of the apparatus of the above-described type that is of a substantially simpler construction that is more economical to manufacture and which retains excellent and reliable working properties throughout a long period of use.